剪切波对时间反转调相的经颅聚焦超声的影响*

为研究颅骨中的剪切波对经颅聚焦超声的影响,该文利用Kelvin-Voigt固体声波方程并结合时间反转法,分别模拟了考虑剪切波和不考虑剪切波时,256-单元平面相控阵为实现超声经颅聚焦所需的相位调控,并将这两种相位调控都分别作用于考虑剪切波和不考虑剪切波时的聚焦情形。对这两种相位调控以及基于它们的经颅聚焦超声场的对比分析结果表明:聚焦深度较大时,剪切波对基于时间反转进行的相位调控影响较小;不过,剪切波对经颅聚焦超声场的强度分布影响较大,忽略剪切波会导致对焦域处声场聚焦强度的高估以及对颅骨附近声能量沉积的低估。

Influence of shear waves on transcranial focused ultrasound using time-reversal-based phase modulations time-reversal-based phase modulations

To study the effect of shear waves in the skull on transcranial focused ultrasound (tcFUS), the Kelvin-Voigt equation combined with the time reversal method is used in this work. Phase modulations of a 256-element planar phased array required for tcFUS are calculated with and without considering shear waves, respectively. And the two phase modulations are both applied to the tcFUS simulations with shear waves included and neglected, respectively. The two phase modulations are compared and the tcFUS fields simulated based on them are analysed. Results show that shear waves have tiny effects on phase modulations based on the time reversal method when the focus is deep in the brain. Nevertheless, shear waves substantially influence the intensity distributions of the tcFUS fields. Neglecting shear waves will lead to an overestimation of the acoustic focusing intensity around the focal region, whilst cause an underestimation of the acoustic energy deposited near the skull.